Vehicles which utilize electric traction motors to drive wheels of a vehicle, whether the electric motor is in a gas-electric hybrid vehicle or a fuel cell powered vehicle, typically use a three-phase AC motor coupled with inverter circuitry that converts direct current from a power source to alternating current. Currently, inverter circuitry generally comprises power transistors mounted on a DBC (direct bonded copper) substrate with integrated bus bars.
As automotive vehicles start, change cruising speeds, accelerate and brake, power demands of electric traction motors driving the vehicles fluctuate over a wide range. Fluctuations in power demand cause temperature changes in power electronics connected to the traction motors. The power electronics include inverter circuitry comprised of different materials with various coefficients of expansion. Accordingly, heat fluctuations can degrade inverter circuitry as the integrated components thereof expand at different rates tending to shift slightly with respect to one another as the components respond to temperature variations. It is necessary to control temperature to keep expansions and contractions of the components within acceptable levels. Currently, this is accomplished by circulating fluids through heat sinks associated with the DBC or by flowing air thereover to absorb and carry away heat. While these approaches currently appear satisfactory, there remains a need to more precisely control the temperature of inverter circuitry over the life of vehicles utilizing traction electric motors in order to sustain reliability, as well as to control power consumption.